An advanced PI control strategy of Dual-Mode-Operation Resonant Converter for Induction Heating

Transcription

1 An advanced PI control strategy of Dual-Mode-Operation Resonant Converter for Induction Heating J.Karthik* 1 ; Ibrahim Shaik 2 & Dr. Abdul Ahad 3 1 M.tech (P&ID) Student Department Of EEE, Nimra College Of Engineering & Technology jaladanikarthik@gmail.com 2 Asst. Professor Department Of EEE, Nimra College Of Engineering & Technology shaikibrahim75@gmail.com 3 Professor & Head Of The Department, Nimra College Of Engineering & Technology ABSTRACT: Induction heating (IH) technology is nowadays widely present in domestic appliances because of its cleanness, high efficiency, and faster heating process. All of these advantages are due to its heating process, where the pot is directly heated by the induced currents generated with a varying magnetic field. As a result, the glass where the pot is supported is not directly heated and, consequently, efficiency and heating times are improved. IH systems are based on dc-link inverters to generate the required alternating current to feed the inductor. Usually, resonant converters are used to achieve higher efficiencies and power densities. As a consequence, in these converters, the efficiency is also reduced in the low-medium output power range. This project presents the use of the half-bridge inverter in two operating modes to achieve higher efficiency in a wide output power range. INTRODUCTION Induction heating is the process of heating an electrically conducting object (usually a metal) by electromagnetic induction, where eddy currents (also called Foucault currents) are generated within the metal and resistance leads to Joule heating of the metal. An induction heater (for any process) consists of an electromagnet, through which a high-frequency alternating current (AC) is passed. Heat may also be generated by magnetic hysteresis losses in materials that have significant relative permeability. The frequency of AC used depends on the object size, material type, coupling (between the work coil and the object to be heated) and the penetration depth. Induction heating allows the targeted heating of an applicable item for applications including surface hardening, melting, brazing and soldering and heating to fit. Iron and its alloys respond best to induction heating, due to their ferromagnetic nature. Eddy currents can, however, be generated in any conductor, and magnetic hysteresis can occur in any magnetic material. Induction heating has been used to heat liquid conductors (such as molten metals) and also gaseous conductors (such as a gas plasma - see Induction plasma technology). Induction heating is often used to heat graphite crucibles (containing other materials) and is used extensively in the semiconductor industry for the heating of silicon and other semiconductors. Utility frequency (50/60 Hz) induction heating is used for many lower cost industrial applications as inverters are not required. Available online: P a g e 603

2 RESONANT CONVERTER They are combination converter topologies or switching strategies that result in zero voltage and/or zero current switchings. Resonant converters use a resonant circuit for switching the transistors when they are at the zero current or zero voltage point, this reduces the stress on the switching transistors and the radio interference. We distinguish between ZVS- and ZCS-resonant converters (ZVS: Zero Voltage Switching, ZCS: Zero Current Switching). INDUCTION HEATING Induction heating is the process of heating an electrically conducting object (usually a metal) by electromagnetic induction, where eddy currents (also called Foucault currents) are generated within the metal and resistance leads to Joule heating of the metal. An induction heater (for any process) consists of an electromagnet, through which a high-frequency alternating current (AC) is passed. Heat may also be generated by magnetic hysteresis losses in materials that have significant relative permeability. The frequency of AC used depends on the object size, material type, coupling (between the work coil and the object to be heated) and the penetration depth. INVERTER A power inverter, or inverter, is an electrical power converter that changes direct current (DC) to alternating current (AC). The input voltage, output voltage, and frequency are dependent on design. Static inverters do not use moving parts in the conversion process. Some applications for inverters include converting highvoltage direct current electric utility line power to AC, and deriving AC from DC power sources such as batteries. CIRCUIT DIAGRAM OF THE PROJECT Fig.1 The series resonant half-bridge applied to induction heating operates at switching frequencies higher than the resonant frequency to achieve zero voltage switching (ZVS) conditions. To reduce switch-off switching losses, a lossless snubber network Cs is added. Typically, class-d operation mode implies that the snubber capacitorcs is much lower than the resonant capacitor Cr. However, if the Available online: P a g e 604

3 class-e conditions are achieved, i.e., ZVS and zero voltage derivative switching (ZVDS) at the turn-off, the operation mode is known as class DE. This operation mode ensures zero switching losses, but the maximum output power is lower than in class-d operation mode. Considering this, a dual-mode resonant converter implementation is proposed in order to improve the efficiency in the whole operating range. Fig. 1 shows the proposed implementation scheme, where electromechanical switches SPST 1 and 2 allow varying the snubber and resonant capacitance in order to change the operation mode. The following sections detail the design procedure for both operation modes, where the superscript D denotes the class-d operation mode and the superscript DE is used for the class-de operation mode. The operation modes of the half bridge inverter, including class-d and class-de operation. Operation Modes The new topology can be effectively broken down into four distinct operating modes, shown in schematic form in Fig. I-IV. STATE I During the first state I, the load current is positive and it is supplied by the high side transistor. STATE II When high-side transistor is deactivated, the switch-off current is used to charge/discharge the snubber capacitors, i.e., the high-side snubber capacitor is charged to the supply voltage, whereas the low-side snubber capacitor is discharged. Available online: P a g e 605

4 STATE III In this state, the load current is also positive, and thus, it is supplied by the low-side diode. STATE IV When the load current becomes negative, it is supplied by the low-side transistor. STATE V As soon as the low-side transistor is deactivated the load current charges the low-side snubber capacitor to the supply voltage, whereas the high-side snubber capacitor is discharged. STATEVI When both snubber capacitors are charged/discharged, the negative load current flows through the high-side diode. Finally, Available online: P a g e 606

5 When the load current reaches zero, the load current is supplied by upper transistor (statei). Class-D operation mode uses configurations I to VI, Where as in class-de operation mode, the configurations II and V, i.e., snubber capacitors charge/discharge, are extended avoiding the use of configurations III and VI, diode conduction. Fig.2 Output current and device activation. (a) Class-D operation mode. (b) Class-DE operation mode. Available online: P a g e 607

6 EFFICIENCY ANALYSIS Power losses in the converter can be divided into two terms: conduction and switching losses. Both of them are caused by the non idealities in the switching devices: nonzero switching times and nonzero on resistance. As a result, switching waveforms in the converter have a direct impact in the entire converter losses. As small snubber capacitors are used in the class-d operation mode, the output current can be considered constant during the charge intervals. As a result, the voltage across the device during the switching becomes linear where IC denotes the switch-off current in the switching devices. Moreover, the required time to charge/discharge the snubber capacitance can be calculated as In the case of the class-de operation mode, the load current is modeled as a linear function that starts in IC, off and ends at zero The class-e switching conditions, i.e., ZVS and ZVDS are achieved in the proposed voltage. The time required to charge/discharge the snubber capacitors TDE snb can be directly obtained. yielding The proposed analytical model for the switching intervals has been validated with simulation results using SPICE simulation tool. The main simulation results are showing a good agreement with the proposed model. Main differences between the SPICE and the analytical model are due to the linear current assumption. These errors have a reduced impact in the output power and conduction losses computation and provide a useful method to predict the required dead time to ensure the correct snubber charge/discharge with reduced computation effort. As a result, the switch voltage is Available online: P a g e 608

7 Fig.3 Simulation of a Closed dual loop Class circuit of RESONANT CONVERTER Fig.4 Closed loop dual Class Switching Waveforms Fig. 4Closed loop dual OUTPUT Voltage and Current Waveform Available online: P a g e 609

8 CONCLUSION In this paper, a novel reconfigurable series resonant inverter topology is proposed in order to improve the efficiency in the whole operating range. It is based on a dual-mode resonant converter where the class-d and class-de operation modes are combined to optimize the efficiency. The analytical results have been verified by means of an experimental prototype. As a result, the presented dual-mode topology is proposed as a cost-effective implementation to improve the overall converter efficiency. REFERENCES [1] O. Luc ıa, J. M. Burd ıo, L. A. Barrag an, J. Acero, and I. Mill an, Seriesresonant multiinverter formultiple induction heaters, Trans. Power Electron., vol. 24, no. 11, pp , Nov [2] H. W. Koertzen, J. A. Ferreira, and J. D. van Wyk, A comparative study of single switch induction heating converters using novel component effectivity concepts, in Proc. IEEE Power Electron. Spec. Conf., Jun./Jul. 1992, pp [3] O. Luc ıa, J. M. Burd ıo, I.Mill an, J. Acero, and L. A. Barrag an, Efficiency oriented design of ZVS half-bridge series resonant inverter with variable frequency duty cycle control, IEEE Trans. Power Electron., vol. 25, no. 7, pp , Jul BIBLIOGRAPHY Jaladani Karthik: pursuing M.Tech in Nimra College of engineering and technology, Jupudi, Ibrahimpatnam. His specialization in power industrial drives. He graduated in Electrical and Electronics Engineering from Swarnandhra College of Engineering & Technology, Seetharampuram, Narsapuram. Mail ID jaladanikarthik@gmail.com Ibrahim Shaik: is currently working as an ASSISTANT PROFESSOR in Electrical and Electronics Engineering department at Nimra College of engineering and technology (NCET) Jupudi, Ibrahimpatnam. He obtained his M TECH degree in power Electronics And Industrial Drives MAIL ID shaikibrahim75@gmail.com DR.Abdul Ahad : Mtech. P.hd (NITK) is an eminent PROFESSOR & HEAD OF EEE, nimra group of colleges. he received M.Tech and was conferred Doctorate from NITK SURATKAL. He is expertised in power electronics, power systems, special machines, Electrical machines& industrial applications. He has over a 15 years of teaching experience.he trains various students for various competitive exams like IES,IAS, GATE, AP GENCO,AP TRANSCO, DISCOMS and no of national competitive exams. He is the chair person of several national and technical symposiums. He published more than 20 international journals and attended several international conferences. His prime interest is in research.to his credit he guided scores of UG AND PG students in their projects and right now he is guiding two P,hd scholars. Available online: P a g e 610